<template>
  <div class="delete">
    <div class="slider">
      <div class="content"
           @touchstart='touchStart'
           @touchmove='touchMove'
           @touchend='touchEnd'
           :style="deleteSlider"
      >
        <slot></slot>
      </div>
      <div class="remove" ref='remove' @click.stop="removeClick()">
        删除
      </div>
    </div>

  </div>
</template>

<script>
  export default {
    data() {
      return {
        startX:0,   //触摸位置
        endX:0,     //结束位置
        moveX: 0,   //滑动时的位置
        disX: 0,    //移动距离
        deleteSlider: '',//滑动时的效果,使用v-bind:style="deleteSlider"
      }
    },
    props: ['itemId', 'index'],
    methods:{
      touchStart(ev){
        ev= ev || event
        //tounches类数组，等于1时表示此时有只有一只手指在触摸屏幕

        if(ev.touches.length == 1){
          // 记录开始位置
          this.startX = ev.touches[0].clientX;
        }
      },
      touchMove(ev){
        ev = ev || event;
        //获取删除按钮的宽度，此宽度为滑块左滑的最大距离
        let wd=this.$refs.remove.offsetWidth;
        if(ev.touches.length == 1) {
          // 滑动时距离浏览器左侧实时距离
          this.moveX = ev.touches[0].clientX

          //起始位置减去 实时的滑动的距离，得到手指实时偏移距离
          this.disX = this.startX - this.moveX;
          // 如果是向右滑动或者不滑动，不改变滑块的位置
          if(this.disX < 0 || this.disX == 0) {
            this.deleteSlider = "transform:translateX(0px)";
            // 大于0，表示左滑了，此时滑块开始滑动
          }else if (this.disX > 0) {
            //具体滑动距离我取的是 手指偏移距离*5。
            this.deleteSlider = "transform:translateX(-" + this.disX*5 + "px)";

            // 最大也只能等于删除按钮宽度
            if (this.disX*5 >=wd) {
              this.deleteSlider = "transform:translateX(-" +wd+ "px)";
            }
          }
        }
      },
      touchEnd(ev){
        ev = ev || event;
        let wd=this.$refs.remove.offsetWidth;
        if (ev.changedTouches.length == 1) {
          let endX = ev.changedTouches[0].clientX;

          this.disX = this.startX - endX;
          //如果距离小于删除按钮一半,强行回到起点

          if ((this.disX*5) < (wd/2)) {

            this.deleteSlider = "transform:translateX(0px)";
          }else{
            //大于一半 滑动到最大值
            this.deleteSlider = "transform:translateX(-"+wd+ "px)";
            this.$emit("moveEnd", {index: this.index})
          }
        }
      },
      removeClick () {
        this.$emit('removeClick', {itemId: this.itemId, index: this.index})
      }
    }
  }
</script>

<style scoped lang="less">
  .slider{
    width: 100%;
    height:103px;
    position: relative;
    user-select: none;
    .content{
      position: absolute;
      left: 0;
      right: 0;
      top: 0;
      bottom: 0;
      background:white;
      z-index: 100;
      //    设置过渡动画
      transition: 0.3s;

    }
    .remove{
      position: absolute;
      width:200px;
      height:103px;
      background:red;
      right: 0;
      top: 0;
      color:#fff;
      text-align: center;
      font-size: 16px;
      line-height: 103px;
    }
  }

</style>
